These codes are the result of try and error.
It means not so good codes.
SaveAppLayout and UpdateLayoutForDPI function should not be callback function.
Add to OnInitdialog
// save current size
SaveAppLayout(this->m_hWnd,(LPARAM)this);
// Resize child windows
// ::EnumChildWindows(this->m_hWnd, SaveAppLayout, (LPARAM)this); // Not necessary
Add to Header
afx_msg void OnSysCommand(UINT nID, LPARAM lParam);
afx_msg void OnPaint();
DECLARE_MESSAGE_MAP()
virtual LRESULT WindowProc(UINT message, WPARAM wParam, LPARAM lParam);
Add to Dlg.cpp
BOOL CALLBACK SaveAppLayout(HWND hWnd,LPARAM lParam)
{
CDPIChangeTestDlg* pParent = (CDPIChangeTestDlg*)lParam;
int iDpi = GetDpiForWindow(hWnd);
// Get current size（at 96 DPI base）
CRect rect;
::GetWindowRect(hWnd, &rect);
pParent->mResMap[hWnd] = rect;
// recalc size
double rate = iDpi / 96;
rect.left *= rate;
rect.top *= rate;
rect.right *= rate;
rect.bottom *= rate;
// resize
SetWindowPos(hWnd, hWnd, rect.left, rect.top, rect.Width(), rect.Height(), SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOMOVE);
return TRUE;
}
BOOL CALLBACK UpdateLayoutForDpi(HWND hWnd, LPARAM lParam)
{
CDPIChangeTestDlg* pParent = (CDPIChangeTestDlg*)lParam;
try {
int iDpi = GetDpiForWindow(hWnd);
// calc current DPI and rate from 96 DPI
double rate = iDpi / 96;
CRect rect = pParent->mResMap[hWnd];
int dpiScaledX = rect.left / rate;
int dpiScaledY = rect.top / rate;
int dpiScaledWidth = rect.Width() / rate;
int dpiScaledHeight = rect.Height() / rate;
// resize
SetWindowPos(hWnd, hWnd, dpiScaledX, dpiScaledY, dpiScaledWidth, dpiScaledHeight, SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOMOVE);
}
catch (...) {
return FALSE;
}
return TRUE;
}
void CDPIChangeTestDlg::OnSysCommand(UINT nID, LPARAM lParam)
{
if ((nID & 0xFFF0) == IDM_ABOUTBOX)
{
CAboutDlg dlgAbout;
dlgAbout.DoModal();
}
else
{
CDialogEx::OnSysCommand(nID, lParam);
}
}
LRESULT CDPIChangeTestDlg::WindowProc(UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message) {
case WM_DPICHANGED:
{
// Resize
UpdateLayoutForDpi(this->m_hWnd, (LPARAM)this);
// Resize Child Windows
// ::EnumChildWindows(this->m_hWnd, UpdateLayoutForDpi, (LPARAM)this); // Not necessary
}
break;
}
return CDialogEx::WindowProc(message, wParam, lParam);
}
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